diff options
author | Laurent Vivier <lvivier@redhat.com> | 2015-08-24 19:29:45 +0200 |
---|---|---|
committer | Laurent Vivier <lvivier@redhat.com> | 2015-09-25 14:52:17 +0200 |
commit | 9491e9bc019a365dfa9780f462984a0d052f4c0d (patch) | |
tree | a4d36d9ecda0e7f129ded20072e572bf9a141785 /hw | |
parent | 8a47d575dfac0f6675e2ac56c5921cc520d021a6 (diff) |
i6300esb: remove muldiv64()
Originally, timers were ticks based, and it made sense to
add ticks to current time to know when to trigger an alarm.
But since commit:
7447545 change all other clock references to use nanosecond resolution accessors
All timers use nanoseconds and we need to convert ticks to nanoseconds, by
doing something like:
y = muldiv64(x, get_ticks_per_sec(), PCI_FREQUENCY)
where x is the number of device ticks and y the number of system ticks.
y is used as nanoseconds in timer functions,
it works because 1 tick is 1 nanosecond.
(get_ticks_per_sec() is 10^9)
But as PCI frequency is 33 MHz, we can also do:
y = x * 30; /* 33 MHz PCI period is 30 ns */
Which is much more simple.
This implies a 33.333333 MHz PCI frequency,
but this is correct.
Signed-off-by: Laurent Vivier <lvivier@redhat.com>
Diffstat (limited to 'hw')
-rw-r--r-- | hw/watchdog/wdt_i6300esb.c | 11 |
1 files changed, 3 insertions, 8 deletions
diff --git a/hw/watchdog/wdt_i6300esb.c b/hw/watchdog/wdt_i6300esb.c index 3e07d44878..a91c8fdad0 100644 --- a/hw/watchdog/wdt_i6300esb.c +++ b/hw/watchdog/wdt_i6300esb.c @@ -129,14 +129,9 @@ static void i6300esb_restart_timer(I6300State *d, int stage) else timeout <<= 5; - /* Get the timeout in units of ticks_per_sec. - * - * ticks_per_sec is typically 10^9 == 0x3B9ACA00 (30 bits), with - * 20 bits of user supplied preload, and 15 bits of scale, the - * multiply here can exceed 64-bits, before we divide by 33MHz, so - * we use a higher-precision intermediate result. - */ - timeout = muldiv64(timeout, get_ticks_per_sec(), 33000000); + /* Get the timeout in nanoseconds. */ + + timeout = timeout * 30; /* on a PCI bus, 1 tick is 30 ns*/ i6300esb_debug("stage %d, timeout %" PRIi64 "\n", d->stage, timeout); |